Fan-motor assembly

ABSTRACT

A fan assembly includes a base which couples to a motor assembly. A shroud couples to the base and encloses a fan therebetween. An airflow conduit is formed between the base and the shroud and is positioned circumferentially around the fan. The airflow conduit terminates at a horn and includes a cross-sectional area which varies circumferentially. The airflow conduit includes a width that varies circumferentially and is largest at the horn.

TECHNICAL FIELD

The present invention is generally directed to motor assemblies. Inparticular, the present invention is directed to a shrouded tangentialfan-motor assembly that increases motor efficiency and air flowcharacteristics. Specifically, the present invention is related to ashroud mountable to a fan end bracket that forms a circumferentiallynon-uniform cross-sectional area.

BACKGROUND ART

Vacuum motors employing a tangential bypass are used in manyapplications such as vacuum manipulators, packaging equipment, bagfilling, cutting tables, appliances and exhaust air removal, to namejust a few. Such vacuum motor designs generally include a cylindricalhousing, or shroud, which encloses a motor-driven fan rotating about anaxis. Air is drawn into the housing via an aperture at the top axialcenter of the housing above the fan. As the fan rotates, the air isaccelerated in the circumferential and radially outward direction. Thehousing provides an outlet located on the side of the fan opposed to theaperture. The outlet is a generally cylindrical opening disposedtangentially on the radially outer edge of the housing so that airtraveling circumferentially along the radial outer edge is expelledthrough the outlet in the tangential direction. Such fans are efficientand have a small profile which enables them to fit in apparatuses whichrequire a thin fan motor assembly.

As with most fan designs, efficiency is an important concern. Currenthousing designs do not direct airflow in its most efficient path withinthe housing. Specifically, unwanted turbulence and dead zones arebelieved to be generated by the uncontrolled path of the airflow fromwhere the air is expelled from the rotating fan to where the air exitsthe outlet. The fan creates significant kinetic energy in the air byimparting tangential speed. The air must be decelerated in a controlledmanner in order to convert the kinetic energy back to pressure. Suddenchanges in cross-section may cause eddies and turbulence whichdissipates the kinetic energy as heat instead of recovering it aspressure. The total pressure (or vacuum) created by the motor/fanassembly is thus negatively affected by allowing air to exit the fan inan uncontrolled manner. Therefore, there is a need to better manage airflow in order to achieve greater fan efficiency. Further, there is aneed to provide air flow management features that are integral to thefan shroud and end bracket. This allows cheaper production, fasterassembly and greater reliability.

Therefore, there exists a need in the art for a shroud and end bracketassembly that directs airflow and increases efficiency.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a first aspect of the present inventionto provide a fan end bracket and shroud that achieves improvedefficiency.

Another aspect of the present invention is to provide a fan assemblycomprising a base which couples to a motor assembly, a shroud whichcouples to the base, at least one fan rotated by the motor assembly andenclosed between the base and the shroud, an airflow conduit formedbetween the base and the shroud and positioned circumferentially aroundthe fan, the airflow conduit terminating at a horn and including across-sectional area which varies circumferentially, and wherein theairflow conduit includes a width that varies circumferentially and islargest at the horn.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of the objects, techniques and structure ofthe invention, reference should be made to the following detaileddescription and accompanying drawings, wherein:

FIG. 1 is perspective view of a fan/motor assembly made in accordancewith the concepts of the present invention;

FIG. 2 is a top elevated view of the fan/motor assembly;

FIG. 3 is a partial cross-sectional view of the fan/motor assembly;

FIG. 4 is a perspective view of the fan assembly;

FIG. 5 is an alternate perspective view of the fan assembly;

FIG. 6 is a top view of the fan assembly;

FIG. 7 is a bottom view of the fan assembly;

FIG. 8 is a top view of a shroud used with the fan/motor assemblyaccording to the present invention;

FIG. 9 is a top view of an end bracket used with the fan/motor assemblyaccording to the present invention;

FIG. 10 is an exploded view of the fan assembly;

FIG. 11 is an alternate exploded view of the fan assembly;

FIG. 12 is a side view of the fan assembly;

FIG. 13 is a sectional view of the fan assembly along lines 13-13 ofFIG. 7;

FIG. 14 is a top view of the motor/fan assembly;

FIG. 14A is a sectional view of the fan assembly along lines 14A-14A ofFIG. 14;

FIG. 14B is a sectional view of the fan assembly along lines 14B-14B ofFIG. 14;

FIG. 14C is a sectional view of the fan assembly along lines 14C-14C ofFIG. 14;

FIG. 14D is a sectional view of the fan assembly along lines 14D-14D ofFIG. 14;

FIG. 14E is a sectional view of the fan assembly along lines 14E-14E ofFIG. 14;

FIG. 14F is a sectional view of the fan assembly along lines 14F-14F ofFIG. 14;

FIG. 14G is a sectional view of the fan assembly along lines 14G-14G ofFIG. 14;

FIG. 14H is a sectional view of the fan assembly along lines 14H-14H ofFIG. 14;

FIG. 14J is a sectional view of the fan assembly along lines 14J-14J ofFIG. 14; and

FIG. 14K is a sectional view of the fan assembly along lines 14K-14K ofFIG. 14.

BEST MODE FOR CARRYING OUT THE INVENTION

A motor/fan assembly is generally indicated by the numeral 10 in theaccompanying drawings. As best seen in FIGS. 1-3, the motor/fan assembly10 includes a motor sub-assembly 12 and a fan sub-assembly 14. It shouldbe appreciated that the motor sub-assembly 12 may be of any suitableconventional construction. In one particular embodiment, themotor-subassembly 12 includes a housing 16. The housing 16 may carry aconcentrically positioned bearing 18 which receives a shaft 20 therein.The shaft 20 carries an armature 22 which is rotatably received within acommutator 24. Shaft 20 further carries a cooling fan 26, which ispositioned on the end of shaft 20 proximate to fan/sub-assembly 14.Cooling fan 26 provides air flow over the internal motor componentspromoting heat dissipation. The motor sub-assembly further includes aplurality of field coils (not shown) as well as a plurality of brushes30. As is known in the art, these motor components interact to causeshaft 20 to selectively rotate. As will be hereinafter described, shaft20 drives the working components of the fan sub-assembly.

Referring now to FIGS. 4-7 and 10-14, fan sub-assembly 14 includes abase 32 coupled to the end of motor sub-assembly 12. Base 32 may begenerally circular and separates the motor sub-assembly 12 from thevarious fan components by sealing around shaft 20 in such a way thatairflow generated by fan sub-assembly 14 is not contaminated by air orother matter from motor sub-assembly 12. Base 32 may be provided with aplurality of ears 34 upon which an associated apparatus may be fastened.Further, one or more mounting projections 35 may extend toward motorsub-assembly 12 to enable coupling thereto.

Base 32 includes a curved outer flange 36 which defines the radiallyouter surface thereof. Outer flange 36 may be provided with a raisedshoulder 38 that projects axially from and circumferentially around theend 40 of outer flange 36. Shoulder 38 is received in thecircumferential groove 42 of a shroud 44. In this manner, shroud 44 isreceived by outer flange 36 forming a generally airtight seal. Shroud44, in cooperation with base 32, forms an enclosed chamber 46 whichreceives the working fan components. The shroud may be frictionallyretained, staked or otherwise secured by fasteners to the base 32.

Base 32 includes an inner plate 48 that extends radially inward fromflange 36 and faces chamber 46. Inner plate 48 includes a shaft aperture50 therethrough. A support ring 52 is provided at the center of innerplate 48 around shaft aperture 50. Support ring 52 extends axially frominner plate 48, defining a boss 54 that extends into chamber 46. Aflange 56 extends inwardly from the axial end of boss 54. A bearing 58is received inside support ring 52 and is adapted to receive and supportshaft 20 which rotates therein. A seal 60 may be captured betweenbearing 58 and flange 56 to prevent contamination of the air passingthrough fan sub-assembly 14. Seal 60 may be in any number of forms andcould utilize the teachings of U.S. Pat. Nos. 5,482,378 and/or6,472,786, both of which are incorporated herein by reference.

Shroud 44 is provided with a cylindrical port 62 which is substantiallyconcentric with the shaft 20. Port 62 is provided to allow working airto enter the fan sub-assembly 14. Shroud 44 encloses a fan 64 thatincludes a plurality of blades 66 that extend radially outwardly. Blades66 may be straight, angled, curved, or oriented in a sunburst pattern.Blades 66 are retained between a disc 68 at a bottom edge of each bladeand a ring 70 at a top edge of each blade, wherein disc 68 has a centralbore 72 permitting the fan 64 to be mounted to the shaft 20. Ring 70 hasan airflow aperture 74 aligned with and approximately the same size asport 62 and in fluid communication therewith.

Fan 64 is spaced and coupled to shaft 20 by a plurality of elements. Aspacer 76 extends through aperture 50 and bears against an inner race ofbearing 58. Spacer 76 may be generally cylindrical and is receivedaround shaft 20. A first washer 78 is positioned between spacer 76 anddisc 68. A second washer 80 is positioned on the opposed side of disc 68and is secured thereto by a nut 82. Nut 82 may be provided at the end ofshaft 20 and may be tightened against second washer 80 which in turnclamps together the inner race of bearing 58, spacer 76, first washer 78and fan 64 so that all turn as one unit with the shaft 20 as it isdriven by motor sub-assembly 12.

Shroud 44 includes a cap 86 that extends radially outward from port 62.Cap 86 is frustoconical and shaped to generally follow the upper profileof ring 70 resulting in minimal clearance therebetween. This preventsunwanted turbulence, leaking and/or bleeding of air moved by the fan 64.To further improve efficiency and prevent leaks, a chamfer 86 isprovided at the radial inner edge of cap 86 that partially receives theupturned edge of ring 70.

A conduit wall 88 extends radially outwardly from cap 86 and terminatesat a downwardly turned lip 90 that includes circumferential groove 42.It should thus be evident that conduit wall 88 of shroud 44 includes anouter profile that mirrors that of the outer profile of flange 36 ofbase 32. The area between conduit wall 88 and base 32 defines a conduit92 through which working air travels during rotation of fan 64. As willbecome evident, the area of conduit 92 grows larger as a function ofcircumferential distance about base 32 from a minimum area (shown inFIG. 14A) to a maximum area (shown in FIG. 14J). Conduit 92 begins atthe minimum area location and terminates at a horn 94, as shownsequentially in FIGS. 14A-14K. Horn 94 includes a lower half 96 formedby base 32 and an upper half 98 formed by shroud 44. Horn 94 issubstantially circular in cross section and extends tangentially frombase 32 and shroud 44. The cross-sectional area of conduit 92 increasesbecause both the width and height increases as a function ofcircumferential location. Thus, the radial distance of flange 36 fromshaft 20 is not constant about the circumference and instead iscurvilinear. In other words, flange 36 varies from a minimum radialdistance (shown in FIG. 14A), to a maximum radial distance (shown inFIG. 14 J). Further, conduit wall 88 includes a radiused or upwardlycurved cross-sectional shape. From minimum point (shown in FIG. 14A)conduit 92 grows wider, as measured by the distance between cap 84 andflange 36. Further, the channel grows taller, as defined by the distancebetween inner plate 48 and the furthest point on conduit portion 88.

When shaft 20 rotates, air is drawn in by the fan 64 into chamber 46 viaport 62. As fan 64 rotates, air is further drawn through airflowaperture 74 and is urged radially outwardly by blades 66. The air flowwhich is ejected radially from blades 66 has both a radial andtangential component. In other words, air particles travel radiallyoutwardly while at the same time spin with the fan 64. Thus, when theair exits the fan 64, if the fan is traveling in a counter-clockwisedirection (as envisioned in the present embodiment), the aircorrespondingly travels circumferentially in a counter-clockwisedirection around conduit 92. Because of the pressure differentialbetween the outside atmosphere and chamber 46, the air exits conduit 92via horn 94. Thus, as described above, air is drawn into port 62 and outof horn 94 upon rotation of shaft 20. Such systems are particularlyuseful in common household vacuums, but may also find applications inmany other fields.

By varying the cross-sectional area of conduit 92 in the mannerdiscussed above, the kinetic energy stored in the moving air can beconverted more completely into static pressure, rather than turbulenceinduced heat, due to the reduction of eddies as the air leaves therotating fan.

Based upon the foregoing, the advantages of the constructions describedabove are readily apparent. In particular, the conduit 92 is configuredto provide a more efficient path for air to travel within fansub-assembly 14. In this manner fan efficiency is increased, thusrequiring less energy to provide the same air flow. As a further result,motor life is extended. Thus, the invention disclosed represents a greatimprovement in the art of fan assemblies.

Thus, it can be seen that the objects of the invention have beensatisfied by the structure presented above. While in accordance with thePatent Statutes, only the best mode and preferred embodiment has beenpresented and described in detail, it is to be understood that theinvention is not limited thereto or thereby. Accordingly, for anappreciation of the true scope and breadth of the invention, referenceshould be made to the following claims.

1. A fan assembly, comprising: a base which couples to a motor assembly;a shroud which couples to said base; at least one fan enclosed betweensaid base and said shroud; an airflow conduit formed between said baseand said shroud and positioned circumferentially around said fan, saidairflow conduit terminating at a horn and including a cross-sectionalarea which varies circumferentially; and wherein said airflow conduitincludes a width that varies circumferentially and is largest at saidhorn.
 2. The fan assembly according to claim 1, wherein said airflowconduit includes a height that varies circumferentially and is largestat said horn.
 3. The fan assembly according to claim 1, wherein saidshroud includes a conduit wall and said base includes an inner wall,said airflow conduit being formed between said conduit wall and saidinner wall, and wherein said conduit wall is curved in cross-section. 4.The fan assembly according to claim 3, wherein said conduit wallincludes a constant cross-sectional radius.
 5. The fan assemblyaccording to claim 1, wherein said base includes an outer flange formingat least part of said conduit, said outer flange being curvilinear. 6.The fan assembly according to claim 1, wherein said base includes anouter flange forming at least part of said conduit, said outer flangeincluding a radial distance from said fan that varies circumferentiallyand is largest at said horn.
 7. The fan assembly according to claim 6,wherein said base includes a conduit wall that mates with said outerflange, said conduit wall including a generally curved cross-sectionalshape.
 8. The fan assembly according to claim 7, wherein said outerflange includes a raised shoulder and said conduit wall includes acircumferential groove, said raised shoulder is received in saidcircumferential groove.
 9. The fan assembly according to claim 3 whereinsaid inner wall is substantially flat in cross-section.
 10. The fanassembly according to claim 3 wherein said shroud includes a portadapted to receive working air, said shroud further including a capextending radially outward from said port terminating at said conduitwall, said cap being frustoconical.
 11. The fan assembly according toclaim 10 wherein said cap includes a chamfer about a radial inner edge,said fan including a ring that is at least partially received in saidchamfer.